Until further orders, turning Charlie will be Stig's primary mission.
He would start by suggesting additional practice, since the performance is so close. If that is accepted, he would try to gain his trust through asking about employment opportunities, since his primary place of employment was poisoned. Basically attempting to get closer to him through whatever seems to work, be it personal, or professionally. He'd pay attention to his mood, since the train mission was, pretty much, foiled. Is Charlie stressed, lack of focus on performance, any window, or opportunity to pick up a way to gain trust. Is the train heist attempt in the paper/major news?